diff options
Diffstat (limited to 'utils/src/main/java')
| -rw-r--r-- | utils/src/main/java/org/onap/policy/common/utils/services/OrderedService.java (renamed from utils/src/main/java/org/onap/policy/common/utils/slf4j/LoggerFactoryWrapper.java) | 36 | ||||
| -rw-r--r-- | utils/src/main/java/org/onap/policy/common/utils/services/OrderedServiceImpl.java | 135 |
2 files changed, 153 insertions, 18 deletions
diff --git a/utils/src/main/java/org/onap/policy/common/utils/slf4j/LoggerFactoryWrapper.java b/utils/src/main/java/org/onap/policy/common/utils/services/OrderedService.java index 6f800015..c5050c83 100644 --- a/utils/src/main/java/org/onap/policy/common/utils/slf4j/LoggerFactoryWrapper.java +++ b/utils/src/main/java/org/onap/policy/common/utils/services/OrderedService.java @@ -1,9 +1,8 @@ /* * ============LICENSE_START======================================================= - * ONAP Policy Engine - Common Modules + * utils * ================================================================================ - * Copyright (C) 2019 Samsung Electronics. All rights reserved. - * Modifications Copyright (C) 2019 AT&T Intellectual Property. + * Copyright (C) 2019 AT&T Intellectual Property. All rights reserved. * ================================================================================ * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. @@ -19,29 +18,30 @@ * ============LICENSE_END========================================================= */ -package org.onap.policy.common.utils.slf4j; - -import org.slf4j.Logger; -import org.slf4j.LoggerFactory; +package org.onap.policy.common.utils.services; /** - * Helper class to retrieve particular types of loggers without storing the logger name everywhere in ths code. + * This is a base interface that is used to control the order of a list + * of services (features) discovered via 'ServiceLoader'. See + * 'OrderedServiceImpl' for more details. */ -public class LoggerFactoryWrapper { - +@FunctionalInterface +public interface OrderedService { /** - * Constructs the object. + * Get sequence number. + * + * @return an integer sequence number, which determines the order of a list + * of objects implementing this interface */ - private LoggerFactoryWrapper() { - super(); - } + public int getSequenceNumber(); + /** - * Get Network Logger. + * Get the name. * - * @return logger instance + * @return the name of the ordered service */ - public static Logger getNetworkLogger() { - return LoggerFactory.getLogger("network"); + public default String getName() { + return this.getClass().getName(); } } diff --git a/utils/src/main/java/org/onap/policy/common/utils/services/OrderedServiceImpl.java b/utils/src/main/java/org/onap/policy/common/utils/services/OrderedServiceImpl.java new file mode 100644 index 00000000..bbd30220 --- /dev/null +++ b/utils/src/main/java/org/onap/policy/common/utils/services/OrderedServiceImpl.java @@ -0,0 +1,135 @@ +/* + * ============LICENSE_START======================================================= + * utils + * ================================================================================ + * Copyright (C) 2019 AT&T Intellectual Property. All rights reserved. + * ================================================================================ + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + * ============LICENSE_END========================================================= + */ + +package org.onap.policy.common.utils.services; + +import java.util.Collections; +import java.util.HashMap; +import java.util.LinkedList; +import java.util.List; +import java.util.ServiceLoader; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +/** + * This class is a template for building a sorted list of service instances, + * which are discovered and created using 'ServiceLoader'. + */ +public class OrderedServiceImpl<T extends OrderedService> { + // logger + private static Logger logger = LoggerFactory.getLogger(OrderedServiceImpl.class); + + // sorted list of instances implementing the service + private List<T> implementers = null; + + // 'ServiceLoader' that is used to discover and create the services + private ServiceLoader<T> serviceLoader = null; + + // use this to ensure that we only use one unique instance of each class + @SuppressWarnings("rawtypes") + private static HashMap<Class,OrderedService> classToSingleton = new HashMap<>(); + + /** + * Constructor - create the 'ServiceLoader' instance. + * + * @param clazz the class object associated with 'T' (I supposed it could + * be a subclass, but I'm not sure this is useful) + */ + public OrderedServiceImpl(Class<T> clazz) { + // This constructor wouldn't be needed if 'T.class' was legal + serviceLoader = ServiceLoader.load(clazz); + } + + /** + * Get List of implementers. + * + * @return the sorted list of services implementing interface 'T' discovered + * by 'ServiceLoader'. + */ + public synchronized List<T> getList() { + if (implementers == null) { + rebuildList(); + } + return implementers; + } + + /** + * This method is called by 'getList', but could also be called directly if + * we were running with a 'ClassLoader' that supported the dynamic addition + * of JAR files. In this case, it could be invoked in order to discover any + * new services implementing interface 'T'. This is probably a relatively + * expensive operation in terms of CPU and elapsed time, so it is best if it + * isn't invoked too frequently. + * + * @return the sorted list of services implementing interface 'T' discovered + * by 'ServiceLoader'. + */ + @SuppressWarnings("unchecked") + public synchronized List<T> rebuildList() { + // build a list of all of the current implementors + List<T> tmp = new LinkedList<>(); + for (T service : serviceLoader) { + tmp.add((T)getSingleton(service)); + } + + // Sort the list according to sequence number, and then alphabetically + // according to full class name. + Collections.sort(tmp, (o1, o2) -> { + int s1 = o1.getSequenceNumber(); + int s2 = o2.getSequenceNumber(); + if (s1 < s2) { + return -1; + } else if (s1 > s2) { + return 1; + } else { + return o1.getClass().getName().compareTo(o2.getClass().getName()); + } + }); + + // create an unmodifiable version of this list + implementers = Collections.unmodifiableList(tmp); + logger.info("***** OrderedServiceImpl implementers:\n {}", implementers); + return implementers; + } + + /** + * If a service implements multiple APIs managed by 'ServiceLoader', a + * separate instance is created for each API. This method ensures that + * the first instance is used in all of the lists. + * + * @param service this is the object created by ServiceLoader + * @return the object to use in place of 'service'. If 'service' is the first + * object of this class created by ServiceLoader, it is returned. If not, + * the object of this class that was initially created is returned + * instead. + */ + private static synchronized OrderedService getSingleton(OrderedService service) { + // see if we already have an instance of this class + OrderedService rval = classToSingleton.get(service.getClass()); + if (rval == null) { + // No previous instance of this class exists -- use the supplied + // instance, and place it in the table. + rval = service; + classToSingleton.put(service.getClass(), service); + } + return rval; + } +} |